Industry is increasingly turning to composite materials that include a polymer and fillers. The polymer generally provides desirable mechanical properties and processability over other materials. Traditionally, fillers are used to provide color or reduce cost, but may augment the mechanical properties and processability of the polymer.
Traditional fillers include milled mineral particulate, or carbon products, such as carbon black and graphite. For example, carbon black and mineral fillers are commonly used in the tire industry. Other mineral fillers are common in building materials and food packing. In general, use of inexpensive filler material, such as carbon black and other mineral fillers, reduces costs and imparts an acceptable color to a product.
More recently, industry is seeking to improve properties of polymer products. For example, barrier properties of polymers are relevant to packaging. For example, oxygen and water vapor in contact with food can increase the rate of spoilage, limiting shelf life. Polymers with good barrier properties can effectively reduce the transfer rate of oxygen and water vapor into the packaged product and extend the shelf life of the product. However, traditional polymer having desirable barrier properties are expensive.
Construction is another area where barrier properties are desirable. Water vapor passing through walls can condense inside the wall and lead to wood rot, mold growth, and pealing of paint. Polymers with desirable barrier properties can effectively reduce the transfer of water vapor through the exterior walls, reducing mold growth and maintenance costs.
Barrier properties are also desired by the tire industry to reduce deflation and prevent moisture buildup within tires. In general, the tire industry generally relies on a multilayer structure including additional material layers to reduce loss of pneumatic pressure. A typical tire is a multilayer structure including an outer tread layer, reinforcement, and an inner butyl liner. Forming, such a multilayer structure is process sensitive and improper processing may lead to delamination of the layer. In recent times, delamination of tread has been cited as a contributing factor to vehicular accidents.
More recently, the tire industry has turned to silica and alumina fillers. For example, publications WO 2006/060468 and WO 2004/090023 broadly disclose use of aluminum-based filler in rubber compositions. However, such aluminum-based fillers have yet to penetrate the tire manufacturing industry to the extent that carbon or silica based materials have. In particular, prior art publications have failed to show significant advantages for use of alumina fillers over carbon black or silica.
As such, an improved composite material would be desirable.